Laser diodes are current driven devices that receive a bias voltage or current from a current source. In conventional circuits (e.g., laser driving circuits) that provide a bias current to a laser diode or other current-driven load, a considerable amount of power may be wasted since the laser diode operates at an operating voltage (e.g., 1.8V) that is less than the bias voltage provided by or to the driving circuit (e.g., 3.3V).
For example, the available supply voltage VCC (for example, 3.3V) is received by the driver, and the laser requires a significantly smaller voltage (for example, from 1.2V to 1.8V, depending on the operating conditions). The difference between the 3.3V supply voltage and the actual operating voltage of the laser (e.g., 1.2-1.8V) is wasted as heat in the transistors of the driving circuit. In this case, the transistor(s) must dissipate 1.5 to 2.1V of power as heat. This dissipation of power is not only wasteful, but it generates thermal energy, which can also adversely affect the operation(s) of nearby circuitry and/or result in a need for an additional cooling element.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.